Patent US4087238A successfully refreshed from Google Patents.
US4087238A
Expired / Lapsed
US
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Method for enhancing the heating efficiency of continuous slab reheating furnaces
Assignee: United States Steel Corp
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Filing: 1976-09-13
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Granted: 1978-05-02
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Expires: 1996-09-13
Abstract
Abstract Significant energy savings are achieved in the operation of reheat furnaces when the preheat zone temperatures are maintained as low as possible consistent with the demands of the hot strip mill. While the benefits of this invention may be realized through manual adjustment, further energy savings are achieved through the utilization of automatic controls and proper scheduling in which slabs of approximately the same thickness are placed into groupings so that a first grouping of tandum slabs enters the furnace, followed by a second grouping of different thickness.
Inventors
- 👤 Lawrence G. Seigel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 14:44
CPC Classifications
C; C21; C21D; C21D9/00; C21D9/0081; F; F27; F27B; F27B9/00; F27B9/14; F27B9/20; F27B9/22; F27B9/30; F27B9/40; F27D; F27D19/00; F27D2019/0028; F27D2019/0034; F27D2019/004; F27M; F27M2001/00; F27M2001/15; F27M2001/1539; F27M2001/1547; F27M2001/1552; F27M2001/156; F27M2001/1565; F27M2003/00; F27M2003/02
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
199 words
In the reheating of slabs to temperatures of about 1150° to 1320° C for further processing in a roll mill, wherein said slabs are elevated to such temperatures by passage through a continuous, co-current fired, pusher type, slab reheating furnace, comprising a preheat zone, a heat zone and a soak zone and heating means associated with each such zone, in which the soak zone is maintained at a median temperature approximately that of a desired exit slab temperature, and the heat zone is maintained at a temperature below that at which the surface of the slabs would melt to a significant extent, but at least that required to impart sufficient heat to achieve said desired exit slab temperature, and wherein the slabs on exiting said furnace are thereafter hot-rolled to semi-finished products, the improvement for enhancing the heating efficiency of said furnace which comprises, (a) maintaining said preheat zone at a median temperature, T p , (i) at least that required to provide a heat-rate sufficient to achieve said desired exit slab temperature, but (ii) no greater than 90% of said soak zone median temperature, T s ; wherein T p and T s are measured in ° C.
Claim 2
Dependent Claim
199 words
In the reheating of slabs to temperatures of about 1150° to 1320° C for further processing in a roll mill, wherein said slabs are elevated to such temperatures by passage through a continuous, co-current fired, pusher type, slab reheating furnace, comprising a preheat zone, a heat zone and a soak zone and heating means associated with each such zone, in which the soak zone is maintained at a median temperature approximately that of a desired exit slab temperature, and the heat zone is maintained at a temperature below that at which the surface of the slabs would melt to a significant extent, but at least that required to impart sufficient heat to achieve said desired exit slab temperature, and wherein the slabs on exiting said furnace are thereafter hot-rolled to semi-finished products, the improvement for enhancing the heating efficiency of said furnace which comprises, (a) maintaining said preheat zone at a median temperature, T p , (i) at least that required to provide a heat-rate sufficient to achieve said desired exit slab temperature, but (ii) no greater than 90% of said soak zone median temperature, T s ; wherein T p and T s are measured in ° C.
Claim 3
Dependent Claim
32 words
The method of claim 1, wherein the actual preheat temperature does not exceed T p + 50° C for a period of time more than about 20% of the total operating time.
Claim 4
Dependent Claim
22 words
The method of claim 2, wherein T p is no greater than 85% of said soak zone median temperature, T s .
Claim 5
Dependent Claim
199 words
The method of claim 1, including the steps of (b) determining the maximum permissible residence time, r 1 , for a slab in its passage through the furnace, (c) determining a preheat temperature, T p1 , associated with said slab, wherein T p1 , falls within the constraints of step (a), (d) adjusting the output of the preheat zone heating means to extablish T p1 , as the temperature of the preheat zone, (e) determining the maximum residence times, r 2 , r 3 . . . for each subsequent slab in its passage through the furnace, (f) utilizing the constraints of step (a), determining T p2 , T p3 . . . , the respective preheat temperatures for each such subsequent slab, (g) adjusting the output of said heating means to establish a higher preheat temperature when a subsequent T p value for a slab in the preheat zone is higher than that established in step (d), and (h) adjusting the output of said heating means to establish a preheat temperature next lowest to T p1 , when (i) time interval r 1 has expired and (ii) when no higher T p value is indicated by step (g).
Claim 6
Dependent Claim
50 words
The method of claim 4, wherein the slabs entering the furnace are scheduled so that for a major portion of the total operating time, the variation in thickness for a grouping of at least 10 successive slabs is not greater than 20% of the average thickness of said 10-slab grouping.
Claim 7
Dependent Claim
19 words
The method of claim 5, wherein said major portion is greater than about 90% of the total operating time.
Claim 8
Dependent Claim
33 words
The method of claim 5, wherein said scheduling is such that at least 20 successive slabs do not vary in thickness by more than 20% of the average thickness of said 20-slab grouping.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-05-01 | 1981-10-31 | 1982-05-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-05-01 | 1985-10-31 | 1986-05-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-05-01 | 1989-10-31 | 1990-05-02 | $7700.00 | Window Closed / Lapsed |